USING VF TERMINAL AS A CLOSED LOOP AND A/F RATIO MONITOR

I found the link to find out if the engine is good or not:

http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&ved=0CDIQFjAC&url=http%3A%2F%2Fwww.autoshop101.com%2Fforms%2Fh27.pdf&ei=Im9OVPzgGoLZmgXtgoKAAw&usg=AFQjCNE31G-KBY05yVRry9YN38qEx7QEfQ&sig2=UUNE1WUogFig7-g-uI0mRw

Its a google document that has instructions on how to pull codes from an older toyota engine. But it also has information on how to test whether the oxygen sensor is giving a true reading or not.

The information is listed near the end of the PDF, look for this title:

USING VF TERMINAL AS A CLOSED LOOP AND A/F RATIO MONITOR and follow the instructions there.

I had the chance to do this recently and I immediately noticed a change in the mileage of the car..... I had a MAP ENHANCER installed (potentiometer from MAP sensor output to ecu) and adjusted  it while looking at the VF pin output until the numbers started changing from 2.5V DC....

From that time on, it was running much better and more fuel efficient.

That was until spark plug 1 went out and I thought I broke something.... I even reset the ecu thinking it may change something and never did until I checked the spark plug..... only number 1 had black dry deposits..... all other ones had the usual tan brown on them.

changed it then regretted messing around with the potentiometers before.... I will need to check again to see if the map setting is dialled down again.